Analysis of the activation energy spectra of the induced anisotropy in amorphous Co58Ni10Fe5Si11B16

Magnetic annealing kinetics for the induced anisotropy and the coercive field in amorphous alloys Co
58
Ni
10
Fe
5
Si
11
B
16
were studied. Spectra of activation energies for "reversible" and "irreversible" annealing processes are determined and discussed in the light of a micromagnetic theory of the induced anisotropy recently proposed [1] on the basis of the thermodynamics of two-level systems [2] : 1. The formation of induced anisotropies in Co
58
- Ni
10
Fe
5
Si
11
B
16
is attributed to an atom pair ordering process around free volumes. 2. "Reversible" annealing processes are characterized by a spectrum of activation energies ranging from 1.8 eV to 2.3 eV. The small pre-exponential factor of τ
o
,R = 6.10
^-16
s points to a localized atomic, thermally activated process. 3. "Irreversible" annealing processes are characterized by small activation energies ranging from 0.5 eV to 1.0 eV. The large pre-exponential factor τ
o
, A = 3-10
^-4
s points to a long-range migration of free volumes leading to an immobilization of atom pairs.